The '06-07 Ducks had the 6th best goal differential that regular season. They played well in the playoffs but they're far from this legendary team that many consider them to be.

Because they lost their starting goaltender and best skater for one month. The same month.

During the injuries to Giguere and Pronger: 2-7-2; -9 goal differential
During the rest of the regular season: 46-13-12; +59 goal differential

That's why they beat the team with the highest goal differential (Ottawa +66; which was lower than Anaheim's pace with Pronger/Giguere) in five games, proving that writing them off historically because of goal differential is a little silly.